Now for the y^2 up top, I figure I'll need to do 3y = 4-u, but I'm not sure how to implement this. When I check my answers with wolfram alpha, they do the same thing up this point, but they put a 9 in front of the sqrt(u).
Something like this:
(-1/3) integral of ( ((4-u)^2) / 9sqrt(u) ) du

And so I am sort of stuck right now, and I'm not sure how to get past this step. Can someone tell me where the 9 is from? Perhaps I'm overlooking some crucial algebraic step.